Clinical Outcomes of an Asymmetric Model of Intrastromal Corneal Ring Segments for the Correction of Keratoconus

Purpose: To evaluate the clinical outcomes of a new model of intrastromal corneal ring segments (ICRSs) (Keraring AS) in patients with keratoconus and quantify subsequent changes in refraction and corneal topography. Methods: This nonrandomized, single-center, retrospective observational study explores the effect of progressive thickness ICRS implantation in patients with keratoconus with a 3-month follow-up. After creating an intrastromal tunnel using a femtosecond laser, 1 or 2 ICRSs of progressive thicknesses (150/250 mu m or 200/300 mu m) and 160-degree arc length were implanted. Changes in uncorrected distance visual acuity, best-corrected distance visual acuity, refractive outcomes, corneal astigmatism, and maximum keratometry readings were recorded before and after surgery. Results: The study cohort consisted of 82 patients (104 eyes) with a mean age of 31.2 +/- 10 years. At 3 months, ICRS implantation significantly improved uncorrected and corrected visual acuities from 0.82 to 0.46 (logarithm of the minimum angle of resolution [LogMAR]) and from 0.31 to 0.21 (LogMAR), respectively (P < 0.001). The mean spherical error reduced from -1.74 diopters (D) to -0.90 D (P < 0.001), and the mean cylindrical error reduced from -4.22 D to -2.01 D (P < 0.001). The manifest refraction spherical equivalent reduced from -3.85 D to -1.91 D (P < 0.001). All topographic parameters were reduced, including maximum keratometry (53.6 D vs. 50.3 D) and keratometric astigmatism (-4.6 D vs. -2.2 D) (P < 0.001). Conclusions: The Keraring AS provides a new, apparently safe, and effective means of improving visual acuity and reducing the refractive error and mean keratometry in eyes with asymmetric keratoconus.